DIMONA, Israel (CNN) -- Israel's nuclear reactor was built with the help of the French more than 40 years ago near the town of Dimona in the Negev Desert.

Nuclear experts say it's the cornerstone of Israel's nuclear arsenal -- where the plutonium is produced for a nuclear program that Israel has never confirmed and never denied.

"There is some speculation based on the amount of the estimated plutonium Israel has produced over the years, but there are many uncertainties about that," says Aver Cohen, author of "Israel and The Bomb."

"Therefore, some people go as little as to say 75 or 90 weapons, and some people go as high as 300 weapons or more."

Most estimates put the stockpile at more than 100 bombs. If true, Israel would be the sixth-ranked nuclear power in the world, just after Britain.

The Israeli government has never deviated from a policy of "nuclear ambiguity" and has never signed the nuclear Non-Proliferation Treaty.

"Israel must appear as a country which has a deterrence," says Israeli opposition Labor Party leader Shimon Peres.

"We never said that we would introduce nuclear weapons. Israel repeatedly declared that we are never going to introduce nuclear weapons - Israel has never made any test of nuclear weapons and we are very careful about it."

Peres is seen as the father of Israel's nuclear bomb. During the 1950s, he won French help to build the reactor at Dimona. For decades, it was referred to as a textile plant.

"Well, textiles are out of business, people are going for high-tech today," Peres says. "But the textile business achieved its basic aim as a deterrent."

In the early years of Israel, a nuclear capability was seen as an insurance policy against a second Holocaust -- the ultimate weapon for a country surrounded by hostile Arab neighbors.

Uzi Even was a young engineer who worked at Dimona.

"It was kind of a pioneering atmosphere because we were really sure that we were doing something that would safeguard the future of our country," says Even.

"Remember that in those days the Holocaust memory was a memory which was still very fresh and we believed that Holocaust can happen again."

Since then, Israel has become a regional superpower. Its conventional military is far superior to that of any Arab country.

And the Israeli military is believed to have air, land and sea capability for launching a nuclear attack.

Recently, Israel took delivery of the new F-16 I -- a long-range fighter which can easily be modified to carry a nuclear payload. It has an unrefueled range of 3,500 miles, capable of reaching, among other countries, Iran.

There's the Jericho medium-range ballistic missile, which may have been adapted to make the three-stage, Shavit satellite launcher.

"And so if you add other stages from the Shavit to the Jericho missile, some people say it can have ranges of up to 3,000 or even 4,000 miles," says retired U.S. Air Force Gen. Don Sheppard.

"So clearly they have the missile and aircraft ability to hit any potential enemy."

Add to that Israel's fleet of three German-built Dolphin class submarines. A recent report in The Los Angeles Times quoted unnamed senior Israeli and U.S. officials saying the subs can now launch cruise missiles modified to carry a nuclear payload. Israel says such modifications are impossible.

"Essentially it is a message that Israel will never be, so to speak, eradicated, removed from the face of the Earth," says Cohen.

"It will be there as an independent nation and even its enemies should recognize that fact."

Vanunu waves to supporters after being freed from prison.

It is believed that Israel has gone on full nuclear alert three times: on the eve of the Six Day War in 1967, during the 1973 Yom Kippur War, and for the entire Gulf War in 1991.

But now, especially after Libya announced it was abandoning it's program of weapons of mass destruction, there's increased pressure on Israel to do the same.

"It is time for Israel to take it's nuclear weapons out of the basement and put them on the table," says Joseph Cirincione of the Carnegie Endowment for Peace.

The argument goes that the neighborhood has changed. Saddam Hussein is no longer a threat, Israel has peace treaties with Jordan and Egypt, and nuclear weapons are no use against Palestinian terror attacks.

After all, you can't nuke Bethlehem, without Israel being exposed to nuclear fallout.

Those who want disarmament say Israel's very existence is no longer under threat, and they say the presence of an Israeli nuclear stockpile, real or perceived, is destabilizing because it promotes an arms race among Arab nations.

"For us it really is a matter of to be or not to be. It is not a simple scope. And everyone that knows Israel knows that Israel is so far from being aggressive," says Peres.

Says Cirincione: "All nations that have nuclear weapons think that they are responsible and it is the other guys who are irresponsible."

For Israelis, even talking about the country's nuclear capability is illegal. Eighteen years ago, Mordechai Vanunu, a former technician at Dimona, revealed all to The Times of London.

"Vanunu in the eyes of the Israeli public is the biggest Israeli traitor there has ever been," says Cohen

He was nabbed in Rome by Israel's secret service and thrown in jail.

"He paid a very high price as maybe a lesson to other people not to follow his tracks," says Even

The Dimona reactor went into operation more than 40 years ago. Under U.S. or European standards, it would probably be shut down by now. Opponents say why not take it off line as part of a bigger deal -- a nuclear-free Middle East.

"In the Middle East, it is an untenable position for the next decade to maintain that no Arab nation can have a nuclear weapon but Israel can," says Cirincione.

"Perhaps we can delay Iran's program, but in the long run as long as Israel has these weapons, others are going to rise up to challenge them. Maybe not next year but certainly next decade."

But how can a country begin talking about disarmament when it can't even acknowledge it has nuclear weapons?

And for most Israelis, locked in a bitter conflict with the Palestinians for more than three years and feeling very insecure, now is the not the time they say to be talking about disarming.

And while the nuclear version of "don't ask, don't tell" may have worked for the last 40 years, the question facing Israel now is how much longer can it keep a bomb in the basement.